By Nir Nave
The Immune System
On 07, Jun 2010 | In Uncategorized | By Nir Nave
The Immune System
Somerset If you raise livestock, you have hopefully, at some point, vaccinated them. But do you know the reason why veterinarians recommend that certain vaccines be given at certain times? Here is some insight into how the immune system works and the reasoning behind some of our recommendations.
Passive immunity. This refers to the initial immunity the calf receives from the cow’s colostrum. Passive immunity can be both a help and a hindrance when http://www.cheapjerseys11.com/ it comes to vaccinating a calf. It is a hindrance since the antibodies that the calf gets from the colostrum may bind to the vaccine and inactivate it.
This is the reason that we used to recommend that calves not be vaccinated until they are 4 months old. By 4 months old, most if not all of the passive immunity has likely waned. Vaccination didn’t hurt the calf, but it was thought that it provided no benefit.
In fact, passive immunity may even help the calf process a vaccine. In addition to the all important antibodies, the calf will also acquire living white blood cells from its mother if it ingests fresh colostrum. These living white blood cells, mainly lymphocytes, confer “memory” to the calf’s immune system. These memory cells may allow the calf to have a booster type response to a vaccine even at a very young age.
Freezing colostrum will kill these cells, thereby eliminating their effect. Dried colostrum replacers obviously have no live cells in them either.
Booster shots. Most good vaccination programs are centered around the booster shot. The booster shot would usually be the second dose of vaccine given in a series. It “boosts” the immunity acquired with the first shot.
It actually does more than give it a boost. In reality, the booster is responsible for nearly all of the actual immunity. Booster shots are given at least two weeks following the initial dose of vaccine but no more than three months later. After three months, the booster effect decreases and it acts more like the first shot.
Here’s how I usually explain the importance of the booster shot. If the first shot gives an immunity factor of 10, the second shot won’t give an immunity factor of 20, but of 100. The first dose of most vaccines won’t give much immunity at all. That is solely the job of the booster.
Local versus systemic. Local vaccines have been around for a long time, but they continue to improve. Local refers to the site of administration, such as intranasal or oral. Systemic vaccines are injected into the animal. Intranasal vaccines are used strategically by a lot of veterinarians because of their safety and effectiveness. They can be difficult to administer sometimes, especially intranasal doses in mature cows.
Locally administered vaccines may actually be boosted with injectable vaccines if the antigens used are similar enough. This is quite convenient because local immunity is, in many cases, superior to systemic immunity, but systemic vaccines are easier to administer.
Modified Live (MLV) versus Killed. If you ever want to see an argument among bovine veterinarians reminiscent of the old “Tastes Great, Less Filling!” commercials, watch a discussion about MLV versus killed vaccines. They are always lively discussions.
MLV vaccines consist of live virus or bacteria which have been altered to not cause disease and generally impart stronger immunity. Protective immunity may be possible often with only one dose, however there can be complications. If some MLV vaccines are given to pregnant cows, the result could be an aborted pregnancy.
There are also concerns about live viruses reverting back to a strain that could make the animal sick, but this is exceedingly rare.
Killed vaccines, on the other hand, have no chance of mutating, because they have been killed. Their immune stimulating potential is generally believed to be inferior to their MLV counterparts and a booster dose is, with very few exceptions, always necessary for protective immunity.
Generating vaccination programs for farms cheap jerseys is not an easy task and should be done in careful consultation with your herd’s veterinarian who is uniquely aware of the specific challenges on your operation. Properly formulated, a sound vaccination program will provide cheap insurance against a devastating infectious disease outbreak.